The present invention relates to thermal reactors for processing semiconductor wafers, and more particularly to a reactor having a domed window with the center of mass equally distributed within the flange portion of the window.
Recent technological progress is closely identified with the increasing miniaturization of electronic circuits made possible by advances in semiconductor processing. Certain advanced processing techniques require exposing a semiconductor structure to a reactant gas under carefully controlled conditions. Examples of such processes include chemical vapor deposition and etching processes. Of particular concern is the uniformity of temperature and gas flow to ensure uniform results, e.g., deposition thickness, across a wafer.
The process of depositing layers on a semiconductor wafer (or substrate) usually involves placing the substrate within a thermal reactor chamber and holding the wafer within a stream of a reactant gas flowing across the surface of a wafer. The thermal reactor is heated by external lamps which pass infra-red radiation into the reactor chamber through upper and lower heating ports. The heating ports are covered by infra-red transparent cover members. The upper cover member is generally characterized by a central window portion and a flange portion. The flange portion serves to support the central window portion in the thermal reactor. During wafer processing stresses are created in the cover member due to a pressure differential across the cover and/or the thermal expansion due to heating of the central window portion. These stresses tend to localize in the flange portion of the cover member.
A cover member for a semiconductor processing thermal reactor is disclosed. The cover member has a central quartz window portion and an outer flange portion. The central window portion has either an inward bow defining a concave outside surface, or an outward bow defining a convex outside surface. The centerline of the central window portion has a radius of curvature which when extended through the flange portion divides the flange portion into an upper flange section and a lower flange section. The upper and lower flange portions having substantially equal masses.